Abstract
We describe a scheme in which a multimode laser diode, with effective coherence length less than 250 µm, is used to illuminate sensors multiplexed in time and with their status read by coherence sensing. Data is presented which shows that the spectral characteristics of the laser light remain essentially unchanged upon direct modulation of the laser injection current or whilst subject to laser feedback. This has allowed the multiplexing scheme network to be implemented without recourse to either a Bragg cell modular or an optical isolator. The technique was applied to measure displacement, strain and temperature. © 1991.

Abstract
A time division multiplexing technique is described in which the frequency of a laser source is modulated with a sampled ramp. The concept is demonstrated with two Mach-Zehnder interferometers in a parallel configuration, separated by a fibre delay line whose length is determined by the characteristics of the sampling waveform. Pseudo-heterodyne processing was used to recover the phase information from each interferometer. The expansion of the technique to a combined frequency and time division multiplexed fibre-optic sensing system is considered.

Abstract
A time division multiplexing technique is described in which the frequency of a laser source is modulated with a sampled ramp. The concept is demonstrated with two Mach-Zehnder interferometers in a parallel configuration, separated by a fibre delay line whose length is determined by the characteristics of the sampling waveform. Pseudo-heterodyne processing was used to recover the phase information from each interferometer. The expansion of the technique to a combined frequency and time division multiplexed fibre-optic sensing system is considered. © 1990.

Abstract

Abstract

Abstract